Tunnel magnetoresistance in magnetic tunnel junctions with a ZnS barrier

We report on the junction magnetoresistance in magnetic tunnel junctions of the hard-soft type with magnetic layers separated by a ZnS barrier. The hard magnetic bottom electrode consists of an artificial antiferromagnetic structure in which the rigidity is ensured by the antiferromagnetic exchange coupling between two FeCo layers through a Ru spacer layer. The samples were grown by sputtering on Si (111) wafers at room temperature and have the following structure: Fe6 nmCu30 nm(CoFe)(1.8 nm)Ru-0.8 nm(CoFe)(3 nm)ZnSx(CoFe)(1 nm)Fe4 nmCu10 nmRu3 nm. The square tunnel elements, with lateral sizes of 10, 20, 50, and 100 mum, exhibit typical tunnel resistance of 2-3 k Omega mum(2) and nonlinear zero field current-voltage (J-V) variation. The most interesting result is the observation of junction magnetoresistance of about 5% at room temperature with a 2 nm thick ZnS barrier. (C) 2001 American Institute of Physics.